The present invention relates to a method of manufacturing a wiring board, a method of manufacturing a semiconductor device, and the wiring board, and more particularly to a method of manufacturing a wiring board which is constituted to enhance a reliability in an electrode pad forming portion of a multilayer substrate, a method of manufacturing a semiconductor device, and the wiring board.
For example, as one of methods of forming a ball in BGA (Ball Grid Array) to be used for connecting a bare chip to a substrate or connecting a package substrate to a mother board, there has been known a manufacturing method of forming a plurality of electrodes on a substrate, then forming a solder resist having holes communicating with the electrodes, fusing, through a heat treatment (a reflow), a solder ball put on an opening of each of the holes and bonding the solder ball thus fused to the electrode in the hole, and forming a solder bump in a protruding state on a surface of the solder resist.
On the other hand, a package having a bare chip mounted on a multilayer substrate has also been developed with a reduction in a size and an increase in an integration in a bare chip (for example, see Patent Document 1).
FIG. 1 shows an example of a structure of a conventional wiring board. In the structure of the board shown in FIG. 1, layers are arranged in such a manner that an outer periphery of an electrode pad 10 is covered with a first insulating layer 12 and an upper surface of the electrode pad 10 is covered with a second insulating layer 13, and a via 14 extended upward from a center of the upper surface of the electrode pad 10 penetrates through the second insulating layer 13 and is thus connected to a wiring layer 16 in an upper part.
The electrode pad 10 has a structure in which an Au layer 17 and an Ni layer 18 are arranged and is provided in such a manner that a surface of the Au layer 17 is exposed from the first insulating layer 12 and the via 14 is connected to the Ni layer 18.
Furthermore, a semiconductor chip is mounted on the electrode pad 10 through a solder bump in some cases, and a solder ball or a pin is bonded to the electrode pad 10 in the other cases. In a wiring board having a multilayer structure, thus, the electrode pad 10 is used as a bare chip loading pad or an external connecting pad.
[Patent Document 1]
    Japanese Patent No. 3635219 (JP-A-2000-323613)
In the wiring board shown in FIG. 1, however, the outer periphery of the electrode pad 10 is comparatively smooth. Therefore, an adhesion to the first insulating layer 12 is small. When heating is carried out through a reflow treatment, there is a possibility that a thermal stress might be applied based on a difference in a thermal expansion between the first insulating layer 12 and the electrode pad 10, resulting in the generation of a delamination in a boundary portion provided in contact with the outer periphery of the electrode pad 10 and a breakage of a part of the first insulating layer 12.
In the case in which a part of the first insulating layer 12 provided in contact with an outer periphery of a corner portion (B portion) of the electrode pad 10 is broken off due to heating through the reflow treatment, furthermore, there is a problem in that a crack 20 might be generated from a corner portion (A portion) of the electrode pad 10 toward the second insulating layer 13.
When there is applied a force for separating a semiconductor chip from the wiring board in a state in which the delamination or the crack is generated after the semiconductor chip is mounted on the electrode pad 10 through the solder bump, moreover, the electrode pad 10 might be separated from the first insulating layer 12.
In consideration of the circumstances, therefore, it is an object of the invention to provide a method of manufacturing a wiring board, a method of manufacturing a semiconductor device, and the wiring board which solve the problems.
In order to solve the problems, the invention has the following means.
According to a first aspect of the invention, there is provided a method of manufacturing a wiring board including:
a first step of forming a resist layer on a support substrate;
a second step of forming, on the resist layer, a tapered opening having a small diameter at the support substrate side and a large diameter at an opening side;
a third step of forming, on an inner part of the tapered opening, an electrode pad having a large diameter at the opening side;
a fourth step of removing the resist layer and forming an insulating layer around the electrode pad and on the support substrate;
a fifth step of forming a via which exposes the electrode pad to the insulating layer;
a sixth step of forming a wiring layer to be electrically connected to the electrode pad on surfaces of the via and the insulating layer; and
a seventh step of removing the support substrate and exposing an end face at a small diameter side of the electrode pad.
According to a second aspect of the invention, there is provided a method of manufacturing a wiring board including:
a first step of forming an insulating layer on a support substrate;
a second step of forming, on the insulating layer, a tapered opening having a small diameter at the support substrate side and a large diameter at an opening side;
a third step of forming, on an inner part of the tapered opening, an electrode pad having a large diameter at the opening side;
a fourth step of forming, on a surface of the insulating layer, a wiring layer to be electrically connected to the electrode pad; and
a fifth step of removing the support substrate and exposing an end face at a small diameter side of the electrode pad.
According to a third aspect of the invention, there is provided the method of manufacturing a wiring board according to the first or second aspect, wherein
the electrode pad has a tilt angle θ to a horizontal plane of a tapered outer peripheral surface which is set to be 50 to 80 degrees.
According to a forth aspect of the invention, there is provided the method of manufacturing a wiring board according to the first aspect, wherein
the fourth step includes a step of roughening a surface including a tapered outer peripheral surface of the electrode pad before forming the insulating layer.
According to a fifth aspect of the invention, there is provided the method of manufacturing a wiring board according to the second aspect, wherein
the third step includes a step of roughening an inner part of the tapered opening before forming the electrode pad.
According to a sixth aspect of the invention, there is provided the method of manufacturing a wiring board according to the first aspect, wherein
the support substrate is formed of a metal;
the third step includes a step of forming a metal layer of the same type as the support substrate between the support substrate and the electrode pad; and
the seventh step includes a step of removing the support substrate and removing the metal layer to cause an exposed surface of the electrode pad to form a tapered opening.
According to a seventh aspect of the invention, there is provided the method of manufacturing a wiring board according to the second aspect, wherein
the support substrate is formed of a metal;
the third step includes a step of forming a metal layer of the same type as the support substrate between the support substrate and the electrode pad; and
the fifth step includes a step of removing the support substrate and removing the metal layer to cause an exposed surface of the electrode pad to form a tapered opening.
According to an eighth aspect of the invention, there is provided a method of manufacturing a semiconductor device using the method of manufacturing a wiring board according to any of the first to seventh aspects, further including:
a step of mounting a semiconductor chip on the electrode pad through a solder bump.
According to a ninth aspect of the invention, there is provided a method of manufacturing a semiconductor device using the method of manufacturing a wiring board according to any of the first to seventh aspects, further including:
a step of mounting a semiconductor chip on a surface at an opposite side to an electrode pad forming surface on which the electrode pad of the wiring board is formed.
According to a tenth aspect of the invention, there is provided a wiring board including:
an electrode pad; and
an insulating layer formed in contact with the electrode pad, wherein
the electrode pad is formed to take a taper shape having a large diameter at an insulating layer side on which the insulating layer is formed and a small diameter at an exposed surface side of the electrode pad.
According to the invention, the outer periphery of the electrode pad is formed to be tapered in such a manner that the support substrate side or the solder connecting side has a small diameter. Therefore, an adhesion of the outer periphery of the electrode pad to the insulating layer can be enhanced, and a delamination is generated with difficulty in a boundary portion of the insulating layer even if a thermal stress generated by a reflow acts, for example. In addition, it is possible to prevent a crack from being generated on the insulating layer from a corner portion of the outer periphery of the electrode pad. Furthermore, the outer periphery of the electrode pad is formed with a gradient having an orientation reduced in a direction of the exposed surface of the taper portion. Therefore, the tapered outer periphery of the electrode pad adheres to the tapered internal wall of the insulating layer so that a bonding strength of the electrode pad can be increased.